Help? 4d56T replaced glow plugs now it doesn't run properly

[lito_onion]

So I got these new glow plugs (12V) to replace the old ones (6.5V) on my Delica, a 2.5L 4d56 turbo-diesel. After the replacement, the car starts but idles incredibly rough and puffs white smoke that smells like unburnt fuel. This problem doesn't go away after several minutes of idling (as it usually does on cold days). So I took the new glow plugs back off and put the old ones back in and...the problem didn't go away! I'm not sure what to do now...any ideas? Before it would start with a bit of puffing and white smoke but that would usually be gone within a minute or so.

[Growlerbearnz]

If you fitted 12V glow plugs to an otherwise stock Delica, then they just wouldn't work. The computer can't run 12V glow plugs without additional modifications to the control circuit. The rough running and white smoke is what you get when you start a diesel without working glow plugs, so it really does sound like that's what's happened.

No idea why reinstalling the old glow plugs hasn't cured the problem- it could be that they were damaged when uninstalled, they're not connected correctly now, or the 12V plugs have blown the computer or control circuit. Plenty of glow circuit troubleshooting advice in the forums.

[FalcoColumbarius]

In addition to Growlerbearnz's observations, you can find that information in L300 Dedicated Category Reference Forum, called "Regarding the ECU" by Morganizer. The glow system I believe works based on the Electronic Control Unit's (ECU) reactance to the plugs' voltage impedance, 'though I'm a painter, not an electrician ~ double check. Not sure what kind of damage putting a twelve volt plug into a six point two volt system would cause but that article should shed some light on the matter. Also, as well as Morganiser, there's another member in this club called "Overlanderjay", often referred to as "site guru" and "electrickery technician". Might be worth looking up for advice.

Also check the Engine Electrical manual in the shop manual downloads.

Falco.

P.S.: I've moved this tread from General Discussion to L300 Technical.

[lito_onion]

Here's the thing though - the previous owner had fitted a manual glow plug switch, meaning that the computer seems to have no part it in it.

I may have also concluded that the glow plugs may not be the issue at all, but something I did during the installation? Today, I cranked the engine without using the glow plugs - no start (obviously). Then I held the glow plugs on for about 4s, and the engine cranks and starts (it's 25C outside), but continues to idle rough. After turning the engine off I can remove the glow plug bus bar and *without* turning on the glow plugs, turn over and start the engine - still runs rough.

The rough running and white puffy smoke seems to be consistent across RPMs (like, no matter the RPM the engine will still skip a few beats and puff white smoke), and regardless of heating status (I had it fired up and idling for about 5 minutes at 25C outside)

[Growlerbearnz]

Ah- the bit about having a manual glow switch was kind of important to understanding the issue.

12V glow plugs will take much longer to warm up than the 6V ones- 6V ones take 3-4 seconds, which is considered super fast for a diesel. 12V glow plugs can take 6-10 seconds to warm up properly. On cold days, you might have to give the glow plugs occasional 6 second bursts while the engine warms up.

That said, it sounds like your glow plugs are working ok. White smoke that continues when the engine is warm suggests a clogged or fuel leaky injector (white smoke just means poor combustion). If it's a leaky injector, the white smoke should get less at higher RPMs.

Are you running waste vegetable oil? When did you last change your fuel filter?

Also, what fault were you trying to cure by changing them in the first place? Was it rough running and white smoke?

[lito_onion]

I've tried holding the button for a little bit longer (about 8s), and the problem persists. The smoke does not reduce at higher RPMS, just goes to a steady cloud instead of puffs.

Not running veggie oil, no idea when the last fuel filter change was.

I was trying to get the new glow plugs in before the winter since I've heard the higher voltage ones would be better for the saskatchewan winters (My new motto is now "If it ain't broke, don't fix it")

I don't think it's the fuel injector because it was literally the moment I changed the glow plugs that the problem started - I had driven the car earlier that day in fact and it ran just fine. The confounding bit is when I changed back to the old glow plugs the problem didn't go away.

[Growlerbearnz]

Hmm. Curious. The white smoke continuing when the engine is warm is the confounding bit- normally cold start smoke will clear up after about 5 minutes of driving, or when the water temperature comes up to normal range.

Have you confirmed that the glow plugs are getting power when you press the button? With a volt meter testing the bus bar, I mean, not just listening for the click. If your relay was bad, or the fusible link in the battery box was blown, you'd still hear the relay click but it wouldn't be supplying any power. Regarding the fusible link- when you changed the glow plugs, did you, by any chance, short anything out? even briefly?

It's possible that there's a bad connection somewhere that's restricting the voltage to the glow plugs, you'd need to test that with a volt meter as well. The usual places that corrode are the fusible link and relay connections.

If you don't have a volt meter, or feel like bypassing the control circuits, you could try applying power directly to the bus bar using a jumper cable for a few seconds, then try starting the engine and see if it's better. Just watch out for all earthed metal bits around the bus bar- you really don't want to melt the fuel pipes by accident.

[lito_onion]

I can confirm the glow plugs are receiving power, I can't confirm that they're ALL receiving power. I can crank the engine on a moderately cold day (around 10C outside) and nothing happens. After I hold the glow plugs for a few seconds, I crank it again and it catches almost instantly.

I may have shorted something out before, but I can confirm that the bus bar is not touching anything when I start the car. I don't have a voltmeter.

My last option now is to just buy new 6.5V glow plugs, assuming I somehow fried both my sets. Anyone have a used set?

[Growlerbearnz]

No need to buy an entire set, just test them individually. If they glow, they're good.

Pretty good video here: https://www.youtube.com/watch?v=4Po_1pNHE1Y

[lito_onion]

Tested the glow plugs, all were fine.

In the end, I bought a new set still off ebay
http://www.ebay.ca/itm/4-Diesel-Glow-Pl ... D100275%26

and the problem still didn't go away - so I figured I had nothing to lose, I started driving the car as per normal and the problem stopped.

Just like that.

So...break your new glow plugs in is the lesson here?